Checking on wiki as Im trying to teach myself about orbits
[tex]\mu = GM[/tex] Standard gravitational parameter
On Wiki I also see that
[tex]\mu = 4\pi^2a^3/T^2[/tex] Standard gravitational parameter

but when I calc them they do not match
using the above orbital elements
I get [tex]\mu = 39.478417604357[/tex] when using [tex]\mu = 4\pi^2a^3/T^2[/tex]
and
[tex]\mu = 132712440018[/tex] [tex]\mu = GM[/tex] this number was taking right from the wiki page for the GM of the Sun.

lol I still dont have enough posts to post a link.

what is the correct Standard gravitational parameter? Am I missing a step or doing it out of order?

Checking on wiki as Im trying to teach myself about orbits
[tex]\mu = GM[/tex] Standard gravitational parameter
On Wiki I also see that
[tex]\mu = 4\pi^2a^3/T^2[/tex] Standard gravitational parameter

but when I calc them they do not match
using the above orbital elements
I get [tex]\mu = 39.478417604357[/tex] when using [tex]\mu = 4\pi^2a^3/T^2[/tex]
and
[tex]\mu = 132712440018[/tex] [tex]\mu = GM[/tex] this number was taking right from the wiki page for the GM of the Sun.

lol I still dont have enough posts to post a link.

what is the correct Standard gravitational parameter? Am I missing a step or doing it out of order?

I have seen that in your first post you state that you have calculated the period T in years. but surely for the formula above you have to use the value in seconds. could you just repeat all the parameters you use as input for the formula together with their units (s, km, whatever) ?

I have less then 15 posts so I cant post the link yet, but the wiki page I am talking about is the same one you posted.

This is right on the page. So I used period in years.
for elliptic orbits: [tex]4 \pi^2 a^3/T^2 = \mu [/tex] (with [tex]a[/tex] expressed in AU and [tex]T[/tex] in years, and with M the total mass relative to that of the Sun, we get [tex]a^3 / T^2 = M[/tex])

I wish that I could post links but on the wiki page wiki/Periapsis_distance

its does not give the units of speed. would it be km/s ?
Periapsis: maximum speed [tex]v_\mathrm{per} = \sqrt{ \frac{(1+e)\mu}{(1-e)a} } \,[/tex] at minimum (periapsis) distance [tex]r_\mathrm{per}=(1-e)a\!\,[/tex]

I have less then 15 posts so I cant post the link yet, but the wiki page I am talking about is the same one you posted.

This is right on the page. So I used period in years.
for elliptic orbits: [tex]4 \pi^2 a^3/T^2 = \mu [/tex] (with [tex]a[/tex] expressed in AU and [tex]T[/tex] in years, and with M the total mass relative to that of the Sun, we get [tex]a^3 / T^2 = M[/tex])

I wish that I could post links but on the wiki page wiki/Periapsis_distance

its does not give the units of speed. would it be km/s ?

The units of speed will depend on the units used. If you use meters, kilograms and seconds, your answer will be in meters/sec. If you use AUs, years and the [itex]\mu[/itex] you arrived at above, your answer will be in AU/yr.
(The reason you got a different value for [itex]\mu[/itex] than wiki was that you were using different base units.)

The units of speed will depend on the units used. If you use meters, kilograms and seconds, your answer will be in meters/sec. If you use AUs, years and the [itex]\mu[/itex] you arrived at above, your answer will be in AU/yr.
(The reason you got a different value for [itex]\mu[/itex] than wiki was that you were using different base units.)

Thank you, your answer made it very clear to me, now that I know about AU/yr vs km/s.